inappropriate pacification of shopkeepers

inappropriate pacification of shopkeepers
A recent report noted that if you are invisible, teleport into a shop,
steal something, teleport out, and then return, the shopkeeper will become
pacified.  This is because the pacification code occurred even if the
shopkeeper already knew your name, as long as the "Welcome" message had not
yet occurred.  Implement <Someone>'s proposed fix: Before pacifying, either
the visitct must be zero (as per old code) or the customer name must
already be known.  And, of course, the customer name must differ from the
current setting.  This skips the pacification code in those situations
where the shopkeeper learned your name but was not happy about it (which is
what visitct > 0 implies, at least initially).

This also deals with an older bug report where you attack a shopkeeper
while outside the shop and then later enter the shop while the shopkeeper
is in it.  hot_pursuit() sets the customer name, and the new check avoids
pacifying the shopkeeper for the same reason as noted above.